The scientific theory, preparation and processing level of materials have become the restrict elements of one nation's scientific and technological progress. The macro properties of the materials depend on their microstructure. Transmission electron microscopy (TEM) is the important equipment characterizing the material microstructure, and as one of the important components of TEM, the sample holder acts the function of loading samples and applying on the samples multi-physics field such as the role of force, thermal, electricity, light and like. At present, higher requirements for TEM and its in-situ technology are put forward with the in-depth study on materials science, and it has become a hot spot of research how to realize the observation of in-situ double-axis tilt of TEM while the external field function is applied on the materials.
According to the mode of tilt, the current commercialized TEM sample holder can be divided into two kinds of single-axis tilt and double-axis tilt. The rotation along the holder shaft is X axis rotation, and the rotation perpendicular to the holder body and the incidence direction of the electron beam is Y axis rotation. Generally, the X axis rotation is realized by goniometer stage for TEM, while the Y axis rotation should be realized by rotating sample loading stage on the sample holder. The current commercialized sample holders, such as: the single-tilt sample holder of Gatan company 613 type, 628 type and 643 type and FEI company SH30 type and SH70 type, can only rotate along X axis and are usually used for the observation of the material diffraction contrast. At the same time, the functions of heating, cooling and mechanical tests (stretch or compression) and like can be realized by some commercialized single-tilt holder, such as Hysitron company PI 95 single-tilt force bar. Although the TEM in-situ mechanical experiment can be carried out and the precise mechanical parameters can be obtained by PI 95, the single-tilt function cannot ensure the electron beam incidence along the low index crystal face of the sample, and therefore clear electron diffraction patterns and high quality and high resolution images cannot be obtained at any time. The samples can be rotated flexibly in two dimensions by the double-tilt sample holder (a certain angle tilt in X and Y axis direction at the same time), and the surface appearance and the diffraction patterns of the crystal structure substance can be observed conveniently, and the crystal structure of the samples can be characterized. Usually the Y axis tilt is mainly realized by two modes: (1) Y axis rotation driven by eccentric crankshaft: a small ceramic ball is embedded at the front end of the eccentric crankshaft and stuck in the center of the sample tilt stage slot, and the tilt stage is pushed to realize the tilt in Y axis direction by the rotation of crank and small ball, which is driven by the rotation of the back-end stepping motor. This mode is used in both of Gatan company 646 type and 652 type sample holders. But the mechanical structure and mount used in this mode are complex, and the small diamond ball embedded at the front end is easily damaged; and the tilt mode leads the entire rotation apparatus occupies almost all the interior space of the sample holder, and additional measuring apparatus cannot be installed; in addition, the phenomenon of mechanical clamping easily appears in large angle tilt due to comparatively complex processing structure. (2) Y axis tilt driven by push rod and slant-plane: in the Double-tiltin situ TEM holder with multiple electrical contacts and its application in MEMS-based mechanical testing of nanomaterials Rodrigo A. Bernal et. al designed a double-axis tilt transmission sample holder, the stepping motor connecting push rod moves back and forth to push the front-end slant-plane of tilt stage, which leads the tilt stage rotates around the center tilt axis, and the tilt of Y axis is realized. The mode increases the available space of the front part of the sample holder, which is suitable for the collocation with a variety of MEMS chips, but the tilt angle of Y axis is restricted largely, and in the actual TEM, the tilt angle of Y axis of the samples can only be in the range of the maximum of ±15 degrees. And larger friction force lies between the push rod and the slant-plane increases its mechanical loss degree and affects its service life. (3) Y axis tilt driven by push rod spring mechanism: such as the in-situ double-tilt sample holder for TEM invented by Wang Yiqian et. al from Qingdao University. Stepping motor or exterior rotation apparatus drives horizontal transmission bar to move along horizontal direction, pushes the right end of direction conversion rod to move downward, further drives the holder to rotate anticlockwise, and the positive and negative tilt of Y axis is realized by the reverse thrust of the spring. The optical fiber and the electrode system can be introduced into the double-tilt sample holder, but its double-tilt push rod and spring also occupy larger volume of the front-end, which is inconvenient for the introduction of other apparatuses, and the stability of the spring is poor and the tilt error is easy to be produced.